The trend of decreasing sizes of feature of ICs can make them increasingly vulnerable to voltages and currents outside of the IC's specified operating range. One type of voltage excursion outside of a specified operation range is electrical overstress (EOS). EOS events can cause permanent damage to small features of ICs such as interconnect metal and contacts.
In order to function properly and avoid damage, ICs need to be protected from voltages outside their specified ranges of operation. Since all external electrical events that may cause damage to an IC cannot necessarily be eliminated external to the IC, a protection circuit integral to the IC may be used to shield sensitive electrical regions and structures within the IC from damage due to EOS events. EOS protection circuits may ensure continued reliable functioning of the IC.